1. Field of the Invention
The present invention relates to a label printing and applying device, preferably of the portable type (which will hereinafter be referred to as a "hand labeler"), and more particularly to a constant pressure printing mechanism for use with the hand labeler. The device makes the printing pressure constant to accomplish the clear printing of labels without any difference in the shading.
2. Description of the Prior Art
Most conventional hand labelers have an integral actuating lever which is comprised of an integrally connected hand lever and printing lever. The actuating lever is pivotally supported on a pivot pin which is positioned between the hand lever and the printing lever. A printing head is mounted to the leading or forward end of the printing lever so that the printing head may be moved toward a printing platen by squeezing of the hand lever. The printing head imprints a label which has been fed onto the surface of the platen.
Because the squeezing force applied to the hand lever of the conventional hand labeler is converted directly into printing pressure against the platen, variations in the squeezing force are liable to produce differently shaded imprints. Moreover, if the hand lever is squeezed especially strongly and swiftly, its impact against the platen causes the printing head to bounce slightly against the platen, which causes double printing on the labels and a resultant deterioration in the printing quality of the labels.
If the conventional hand lever is squeezed for a long time, the types of the printing head are held in contact with the label surface for such a long time that the imprints become too thick. If, on the other hand, the hand lever is released too quickly, the types leave the label surface so quickly that the imprints become too light. Thus, differently shaded imprints are caused by variations in the length of the squeezing time.
Even unclear labels obtained by printing operations by hand labelers of the above type are considered to barely succeed in performing their functions if the imprints can only barely be read out both by customers when they purchase commodities and by clerks when they calculate the sales. In recent years, however, clerks taking care of registers have been replaced by optical character reader mechanisms. A reader is connected with an electronic computer system. This enables use of the POS (i.e., Point-of-Sale) system, in which the numerals or characters (e.g., bar codes or OCR symbols) on the labels are automatically read out to record and process in the computer system relevant business information, such as the stock, sales, sales analysis for each commodity or profit calculation. In a machine controlled POS system, it is required that the imprints on the labels be clear at all times.